A known fixing device includes an endless belt rotating about its axis, a ceramic heater disposed inside the endless belt and having a rectangular shape elongated in an axial direction of the endless belt, and a pressure roller sandwiching the endless belt against the ceramic heater to form a nip portion. A sheet is conveyed in a conveying direction while being sandwiched by the endless belt and the pressure roller, and is separated from the endless belt at a downstream end of the ceramic heater.